Hydromorphone and hydrocodone are opioid analgesic drugs available in the market and both are generally used for relief of moderate to severe pain in patients where an opioid analgesic is appropriate. Hydrocodone is the most frequently prescribed opiate in the United States. Although hydromorphone is two to three times more potent than hydrocodone, it is also at least two to four times more expensive than hydrocodone. The higher cost of hydromorphone is due to the difficulty of its production. Despite this, however, prescriptions for hydromorphone products increased from about 0.47 million in 1998 to about 1.83 million in 2006. The aggregate production quota for hydromorphone as established by DEA increased from 766 kilograms in 1998 to 3,300 kilograms in 2006.
One of the current methods for the production of hydromorphone or hydrocodone involves a two-step oxidation/reduction route from morphine or codeine, respectively. This method, however, is expensive and inefficient. The reaction is carried out in the presence of a strong base such as potassium tert-butoxide, and under this severe reaction condition, dimers are formed as impurities that are very difficult to remove. Another production method utilizes isomerization of morphine to hydromorphone in the presence of a late transition metal and metal chloride. The method was originally developed in Germany a half century ago and modified a decade ago. Theoretically, the catalyst is formed in situ under a severe reaction condition in which the conversion between metal and metal ion occurs. Even though the isomerization of morphine to hydromorphone proceeds well, the side reactions of catalytic dimerizations and formation of dihydromorphine by reducing morphine or hydromorphone are also significant. Each of the current production methods generates only a moderate yield in an industrial environment, typically 40%-60% mole/mole even after optimization, due to the difficulty in the removal of impurities. Thus, there is a need for new processes for producing hydromorphone at lower costs, with higher yield and higher purity to meet the increasing demand for hydromorphone.